Cam operated circuit breaker



Aug. 24, 1948. g, D, LAKE E1- AL 2,447,806

` cm oPERA'rEn cIRcuIT BREAKER Filed oct.' 1'1, w46

MMM/70N [L www Y O/Fr MDI. .T w im mD/AW A mm CM Patented Aug. A24, 194s UNITED STATES PirrrtmfV Iomer:

' amant- CAM oraaafmn cmourr nimma Clair D. Lake, Binghamton, and Michael Flehl,

Endicott, N. Y., assixnors to International Business Machines Corporation, New York, N. Y., a corporation oi.' New York Application october 11,19, serum. '102,156

More specically, this invention pertains to cam operated, electrical circuit breakers for use in high speed electrical accounting machines wherein a plurality of such devices is operated by a common cam shaft.

It is well known that when a pair of electrical contacts is opened and closed with great rapidity a tendency exists for the contacts to' vibrate or to oscillate. Itis also well known that this tendency, sometimes referred to as contact bounce, is more prevalent where a pair of contacts is biased under spring tension which is a means frequently used for holding contacts normally closed` or normally open. A common method for'reducing contact bounce betweenv contacts of this type is by increasing the size or the tension of the spring which biases the contacts; however, as the size or tension of the spring is increased limitations are reached, especially in devices such as high speed electrical accounting machines. y

It is acommon practice in electrical accounting machines to pass record cards between a plurality of sensing contacts or brushes and a contact roller whereby la perforation in. a card is sensed when a brush makes electrical contact with the roller through the perforation -wlien it occurs. Since the current flowing in such a circuit frequently reaches a valuenot capable of being properly interrupted by the brush and contact roller, circuit breakers are normally includedin the circuit. These circuit breakers are adjusted to close the circuit after the brush contacts` the roller and to open the. circuit before the brush breaks contact with the roller. Consequently, it is essential that a circuit breaker so employed isf-.free from contact bounce otherwise the purpose of its inclusion is defeated. As the speed of operation of an electrical accounting machine becomes higher and higher as a result of technical improvements it is even more essential that the circuit breaker components maintain proper circuit continuity.

It is, accordingly, 'an object of this invention to provide improved means for making and breaking an electrical circuit-with great rapidity and maximum reliability.

It is a further object of this invention to provide a cam operated. electrical circuit breaker of improved construction 4and arrangement of parts whereby tendencies for its contacts to vis claims. (o1. zoo-153) v 2 brate or to oscillate during high speed operation are eliminated.

. Other objects of theinvention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the 'principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawing:

Fig. 1 is a front elevation view of the circuit breaker having a cut away portion and a fragmentary view of a coacting actuating cam.

Fig. 2 is a fragmentaryview of Fig. 1 illustrating the operation of the circuit breaker.

Fig. 3 is a fragmentary view of Fig. 1 illustrating further the operation o! the circuit breaker. i

lWith reference to the drawing. a rocker arm I0 is pivotally connected with an insulating contact supporting block I I by way of a shaft I2 and a bearing I3. The .block II is slotted to permit the rocker arm I0 to be partially contained within it. One end of the rocker arm IIl is provided with a shaped nose I4 which is biased by a spring I5 normally to urge the nose I4 upwards to contact an actuating cam I6 mounted onga shaft I1 which rotates in a clockwise direction. The

lspring I5 is contained in recessed wells respectively in the arm I0 and the block II and also tends to rotate the arm I0 in a clockwise direction. On the other end of the arm I0 is iastened an operating lug I8 by means of an insulating strip I9 which is pinned respectively tothe arm I0 and the lu'g I8 by the pins 20.

Recessed partially in the block II and secured to the block by the screws 2| yis a contact holder 22 containing a slidable plunger 23 having a contact 2l at one end. The opposite end of the plunger 23 is hollowed to contain spring 25 which continually urges the plunger 23 to the left as viewed in Fig. 1. A notch 26 is cut into the plunger 23.

The lug I8 is arranged to engage the notch 2B so that a counterclockwise rotation of the arm I0 will cause the plunger 23 to be moved to the right (as seen in Fig. 1) and the spring 25 to be com- 'pressed- Another contact holder 21 is partially recessed in the block I I and secured to the block by a screw 28. A l-xed contact 29 is inserted in a hole in the holder 21 and is retained by set screw 30. The fixed contact 29 is arranged to be coaxial with the contact and the plunger 23,

the last two mentioned components forming the movable contact of the circuit breaker. Tapered sockets 3| are provided inv both the holder 22 and the holder 21 for attaching wires or cables. The

l block Il is provided` with-mounting holes 32 by which the circuit'breaker can be attached..

The nose I4 of the rocker arm I0 is provided with a ilat angle surface I4a, the degree of angularity being critical and is determined experimentally, depending upon the speed at which the circuit breaker is to be operated. The lug I8 and the notch 2B are so constructed to provide a certain amount of play between them, the amount of play being critical and is determined experimentally, depending upon the speed at which the circuit breaker is to be operated.

Operation of the'present invention can be understood by reference to Fig. '1 of the drawing where the circuitbrea'keris shown with its movable contact held open by the lug I8 due to the point of the nose I4 of thearm l0 riding on the i'ace of the cam I6. The plunger 23 is at this time held in its extreme right hand position, and the springs I6 and 25 are compressed. vAs the cam I8 rotates clockwise the nose I4 of the arm Il) rides along the cam face until a condition is obtained as in Fig. 2. At that time the point of the nose I4 drops off the cam I6 and the face I4a maintains contact with the cam, the arm I rotating clockwise so that the lug .I8 permits the plunger 23 to be moved to the left urged/by the tension in the spring 25 to close the contact 24 against the contact 29. The lug I8 bears against the right side of the notch 28 when the contacts close.

Following the law of reaction the maximum tendency for "contact bounce" in a pair of closing contacts occurs when the contacts impinge or shortly thereafter. In the present invention these tendencies are counteracted by a further operation of the circuit breaker as follows:

When contact 24 impinges againstcontact 29 .the face I4a contacts the receding lobe of cam IB. An instant later (see Fig. 3) all contact befollower having a rst portion engaged with the movable contact so as to have play between them second portion of the follower being shaped to so tween the cam I6 and the arm I0 is severed as` the cam continues to rotate. clockwise under the urging of the spring I5 until lug I8 travels vto the left finally being arrested by encountering the left side of the notch' 26.

Consequently any tendency for the plunger 23` to reactA or to bounce to the right as a result of impinging its .contact 24 against the fixed contact 29 is compensated. As hereinbefore stated. the angularity of the face I4a and the size of Army I0 rotates coact with the cam at its drop shoulder as to produce a graduated release of the follower from the operating face of the cam thereby delaying the action of the second said spring for taking up of the said play between the said first portion and the movable contact until it has fully engaged the said stationary contact to compensate for4 rebounding of the said contacts.

2. In a cam operated electrical circuit breaker, a stationary contact and a movable contact operable to engage the stationaryv contact, a pivoted cam follower for operating the said movable contact, the said follower having two arms, the first arm engaging the said movable contact and the second arm engaging the said cam to restrain thev movable contact from engagement with' the stationary contact until a drop in the cam occurs, a first resilient means associated with the movable contact biasing it to engage the stationary contact, a 'second resilient means associated with the said second arm biasing the said follower to operate to engage the said movable contact with the said stationary contact, and the said second arm arranged to eifect release of the said follower from the said cam when a drop occurs so that the movable contact engages the stationary contact under the influence oithe said rst resilient I means and then under the influence of the comthe notch 26 are determined before hand and so' arranged to secure the desired effect commensurate with the speed of operation of the circuit breaker. Minor vadjustments are obtained by adjustment of the fixed contact 29 which can be held in various fixed positions by means of the set screw 30.

While there have been shown and described and pointed out'the fundamental novel features of the invention as applied to a preferred embodiment. it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation maybe made by those skilled in the art without departing from the spirit of the invention. It is the intention. therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A circuit controlling device comprising a relatively stationary contact, a contact movable toward -the stationary contact into engagement bined said first and second resilient means whereby tendencies for the said contacts to disengage are eliminated.

3. Circuit controlling apparatus comprising an insulated support having a slotted portion, a rocker arm within the slotted portion pivotally mounted to the said support, a rotatable cam shaft having attached thereto a cam arranged with an abrupt drop, a holder on the said support l provided to receive a contact, a contact fittedl into the said holder, means for fixing the said contact in the said holder in one' of several positions, a second holder on the said support to receive a cylindrical plunger, a notched plunger mounted slidably in the said second holder, a contact on one. end of lthe said plunger capable of engaging the fixed contact, a spring coacting with the other end of the said plunger and the said second holder to bias the plunger contact into engagement with the said fixed contact, one end of the said rocker arm engaging with play the said plunger at the said notched portion and another end of t Y s tact under the inuence o! the saidpiunger spring and thereafter to release the said arm abruptly from the said cam so that the said second spring takes up the said Play at the notched portion of the said plunger to counteract rebound tenden- Number l 1 176-794 cies of the seid contacts. Y f

- ommn. LAKE.- 1'807'376 MICHAEL FIEHL.

REFERENCES CITED n Number The following references are of record in the 62,076` tile of this patent: 301,933

Great Britain Ffh. 27. 1930 

